patch-from in single-thread mode performs worse than multithreaded #4093
Description
Describe the bug
The man page states:
Note: for all levels, you can use --patch-from in --single-thread mode to improve compression ratio at the cost of speed.
I tried that. This is not true.
To Reproduce
Steps to reproduce the behavior:
- use
--patch-fromwith-T8 - use
--patch-fromwith--single-thread - see
--single-threadperform worse
Expected behavior
--single-thread should not perform worse.
Screenshots and charts
❯ zstd --long -T8 --progress --ultra -22 --patch-from archlinux-2024.06.01-x86_64.iso archlinux-2024.07.01-x86_64.iso
archlinux-2024.07.01-x86_64.iso : 25.03% ( 1.09 GiB => 280 MiB, archlinux-2024.07.01-x86_64.iso.zst)
5m 53s
❯ zstd --long --single-thread --progress --ultra -22 --patch-from archlinux-2024.06.01-x86_64.iso archlinux-2024.07.01-x86_64.iso
archlinux-2024.07.01-x86_64.iso : 46.21% ( 1.09 GiB => 517 MiB, archlinux-2024.07.01-x86_64.iso.zst)
7m 9sDesktop (please complete the following information):
- OS: CachyOS
- Version 1.5.6
- Other relevant hardware specs: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
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